40 PEARLS [CH. 



The Reproductive System. 



The last system in the body to which we shall 

 allude is the one comprising those organs upon 

 which the upkeep of the race depends. In the pearl 

 oyster the sexes are separate, that is to say, an 

 individual is either male or female. (In the scallop, 

 both male and female organs are found in each 

 individual.) 



There is however no difference to the eye in the 

 external appearance of male and female oysters ; the 

 sex can only be determined by examining closely 

 the organs of reproduction inside the body. The 

 organs themselves are rather diffuse, and consist of 

 hundreds of branched tubules which cover the stomach, 

 the digestive gland, and the intestine. The tubules 

 open into little sacs, and in these the eggs or sper- 

 matozoa are formed, according to the sex. The 

 tubules join up to form ducts which open into each 

 other until they form a large duct on each side which 

 opens to the exterior. When the reproductive organs 

 are mature, the eggs or spermatozoa are shed into 

 the sea. They pass out of the shell and float about 

 in the water in which the animals are living. As the 

 spermatozoa are developed in countless numbers and 

 as the pearl oysters are gregarious, there is every 

 chance of a sperm meeting an egg. Fusion of the 

 two then takes place and fertilisation is accomplished. 



